Magnetoelectronics devices, spin electronics devices, and spintronics devices are synonymous terms for devices that use the effects predominantly caused by electron spin. Magnetoelectronics effects are used in numerous information devices, and provide non-volatile, reliable, radiation resistant, and high-density data storage and retrieval. The numerous magnetoelectronics information devices include, but are not limited to, magnetic random access memory (MRAM), magnetic sensors, and read/write heads for disk drives.
Typically, a magnetoelectronic device, such as a magnetic memory element, has a structure that includes multiple ferromagnetic layers separated by at least one non-magnetic layer. In the magnetic memory element, information is stored as directions of magnetization vectors in the magnetic layers. Magnetization vectors in one magnetic layer, for instance, are magnetically fixed or pinned, while the magnetization direction of the other magnetic layer is free to switch between the same and opposite directions that are called “parallel” and “antiparallel” states, respectively. In response to parallel and antiparallel states, the magnetic memory element represents two different resistances. The resistance has minimum and maximum values when the magnetization vectors of the two magnetic layers point in substantially the same and opposite directions, respectively. Accordingly, a detection of change in resistance allows a device, such as an MRAM device, to provide information stored in the magnetic memory element. The difference between the minimum and maximum resistance values divided by the minimum resistance is known as the magnetoresistance ratio (MR).
One type of magnetic memory element, a magnetic tunnel junction (MTJ) element, comprises a fixed ferromagnetic layer that has a magnetization direction fixed with respect to an external magnetic field and a free ferromagnetic layer that has a magnetization direction that is free to rotate with the external magnetic field. The fixed layer and free layer are separated by an insulating tunnel barrier layer that relies upon the phenomenon of spin-polarized electron tunneling through the tunnel barrier layer between the free and fixed ferromagnetic layers. The tunneling phenomenon is electron spin dependent, making the magnetic response of the MTJ element a function of the relative orientations and spin polarization of the conduction electrons between the free and fixed ferromagnetic layer.
The tunnel barrier layer is important to the performance of the MTJ element, as the MR is strongly dependent on the tunnel barrier quality. In particular, the surface smoothness of the tunnel barrier plays a critical role in making a high-quality MTJ device. Typically, surface roughness of the tunnel barrier leads to a reduction of MR due to non-tunnel current flow through the barrier or over oxidation of high spots in the bottom ferromagnetic layer, which consequently reduces reliability and thus process yield in MTJ device fabrication. Further, because future generations of magnetoelectronic devices, such as MRAMs, will be scaled to smaller sizes, thinner tunnel barrier layers will be required. Accordingly, as the tunnel barrier layers become thinner in future devices, the surface smoothness will become even more important.
Accordingly, it is desirable to provide MTJ elements having tunnel barrier layers with reduced surface roughness. In addition, it is desirable to provide a process for fabricating an MTJ element having improved electrical properties. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.